The wedged-recovery heartbeat watchdog (line 2526) calls
_notify_fatal_error() directly from the heartbeat task. disconnect()
cancels _polling_heartbeat_task unconditionally (no current_task guard,
unlike _polling_error_task). Same bug class as #68406: the child
disconnect cancels the heartbeat parent before the runner can queue
reconnect.
Widen _handoff_polling_fatal_error() to also clear
_polling_heartbeat_task when it is the current task, and route the
heartbeat watchdog call site through the handoff helper.
Co-authored-by: Imgaojp <6065749+Imgaojp@users.noreply.github.com>